This invention relates to a roll-back vehicle transport apparatus which defines a low approach angle with the ground. In addition, the disclosed invention is efficiently slidably supported for movement between transport and loading positions.
Modern devices for transporting vehicles are often of the roll-back type which include a vehicle support surface supported upon a truck bed frame. The support surface is pivotable relative to the bed frame between a transport position, at which it extends parallel to the bed frame, and a loading position, at which it extends at an angle relative to the bed frame and contacts the ground, defining an approach angle. A vehicle to be transported upon the support surface is moved upwardly onto the support surface, and the support surface is then returned to the transport position.
Some problems do exist with roll-back devices. The approach angle is often somewhat steep and it is sometimes difficult to move vehicles having a low ground clearance onto the support surface. Also, when the vehicle to be transported is being moved onto the support surface, it must be moved through the approach angle against the force of gravity. For these reasons it would be desirable to decrease the approach angle that the support surface defines with the ground when in the loading position.
In the prior art, a single point on the support surface contacts the ground and defines an approach angle for a vehicle to be transported on the roll-back apparatus. This point contact may result in undesirable stress on the support surface, since the entire weight of a vehicle to be transported is supported at this single point. For this reason it would be desirable to have contact between the support surface and the ground over a greater area.
A typical roll-back support surface includes a subframe which actually pivots relative to the truck bed frame, and a deck portion slidably supported on the subframe. A hydraulic cylinder is driven to pivot the subframe and deck relative to the truck bed frame. The deck portion extends further forward than the subframe when in the transport position. To move the deck to the loading position, it is first driven rearwardly relative to the subframe. Once the deck arrives at the rearward position, the subframe is driven to pivot relative to the truck bed frame. The deck portion is now positioned rearwardly relatively to the subframe and contacts the ground.
When the deck moves relative to the subframe it is often carrying the weight of a vehicle. Thus, it is necessary to adequately support the deck for slidable movement relative to the subframe. Prior art devices have used slide pads fixed to the subframe to provide a sliding bearing for the surfaces between the subframe and the deck.
Problems exist with these prior art arrangements in that slide pads are relatively expensive and become worn relatively quickly. The areas of sliding contact between the subframe and the deck change as the deck moves relative to the subframe, and it has been necessary to have slide pads placed throughout the length of the subframe. It would be desirable to use slide pads of less length than the entire length of the subframe, such that less of the expensive slide pad material is required.
It is an object of the present invention to disclose a roll-back apparatus in which the deck defines both a relatively low approach angle relative to the ground, and in which the deck contacts the ground over a relatively great area compared to prior art arrangements. In addition, it is an object of the present invention to disclose an arrangement in which the deck is slidably supported relatively to the subframe with relatively short, long-lasting slide pads.